Dual evaporator air cooling apparatus



Oct. 26, 1954 5 sc w 2,692,481

DUAL EVAPORATOR AIR COOLING APPARATUS Filed March 16, 1951 2Sheets-Sheet l a FIG. I

ROOM AIR i ROOM AIR W 80 TEMPERATURE 70- TO- 60- 60- EVAPORATOR E(TEMPERATURE 50- 5( I 40- 4o- EVAPORATOR TEMPERATURE zofiuu-mlmm nimumHRS. 5 l0 HRS. IO 20 84 4 H95 FIG.

F|G.2 BY

Oct. 26, 1954 s. M. SCHWELLER 2,692,481

DUAL. EVAPORATOR AIR COOLING APPARATUS Filed March 16, 1951 2 Sheets-Sheet 2 Patented Oct. 26, 1954 DUAL EVAPORATOR AIR COOLINGAPPARATUS Sylvester M. Schweller, Dayton, Ohio, assignor to GeneralMotors Corporation, Dayton, Ohio, a

corporation of Delaware Application March 16, 1951, Serial No. 215,985

6 Claims.

This invention relates to refrigerating apparatus and more particularlyto air conditioning apparatus of the type used for room cooling and roomdehumidification.

Air conditioning apparatus is customarily designed to operate down to acertain air temperature and the smallest size of evaporator is selectedwhich will perform properly down to such a temperature. It sometimeshappens that some individual users desire to operate at temperaturesbelow those for which the apparatus is designed. Under such conditionsthere is often an accumulation of frost and ice upon a portion of theevaporator which gradually builds up as the adverse'conditions continueuntil the operation of the air conditioning apparatus becomes seriouslyimpaired.

- It is an object of my invention to provide a control device which willprevent this accumulation of frost and ice upon the evaporating means ofair conditioning apparatuses.

It is another object of my invention to provide a thermostatic controlresponsive to temperature upon the coldest part of the evaporator whichwill stop refrigeration in the evaporator until the temperature of theevaporator rises sufficiently high to prevent frosting and theaccumulation of ice.

These objects are obtained in one form of my invention by providing athermostatic switch in series with one compressor motor of a dual airconditioning room cooling apparatus. This thermostatic switch has itsthermostat bulb connected to the coldest portion of the lower evaporatorand in particular the bulb is clamped to the lowermost return bendnearest the exit of the air stream drawn through the evaporator. Thisswitch opens the compressor motor circuit at about 35 F. and does notclose the circuit until about a temperature of 60 F. is reached. Inanother form, primarily designed for dehumidification, a thermostatswitch is connected in series with the motor compressor unit and has itsbulb clamped to the coldest portion of a spiral-shaped evaporator. Thiscoldest portion is located on the second and third outermost coils ofthe spiral evaporator. This thermostat is set to open a compressor motorcircuit at about 28 F. and to close the circuit at about 45 F.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to theaccompanyingdrawings, wherein a preferred form of the present invention is clearlyshown.

In the drawings:

Fig. 1 is a vertical sectional view, partly diagrammatic, of a windowtype room cooling air conditioning apparatus embodying one form of myinvention;

Fig. 2 is a fragmentary enlarged view of a portion of the lowerevaporator showing the clamping of the thermostat bulb to the returnbend;

Fig. 3 is a temperature-time graph showing the effect upon theevaporator temperature and the room air temperature by operation of mycontrol;

Fig. 4 is a similar temperature time graph for the form of airconditioning apparatus shown in Fig. 5;

Fig. 5 is a vertical sectional view, partly diagrammatic, of an airconditioning apparatus primarily designed for dehumidifying a room orbasement and;

Fig. 6 is a fragmentary View showing the particular clamping arrangementof the thermostatic bulb upon the evaporator. 4

Referring now to the drawings and more particularly to Fig. 1, there isshown a window air conditioner 22 adapted to be placed through theopening in the wall 20 of a room or other enclosure to be cooled. Thisparticular apparatus is of the dual type and includes a lower evaporator24 and an upper evaporator 26 located directly over the lower evaporator24. These evaporators are both of the cross fin and tube type and arelocated directly adjacent the room air inlet opening 28 0f the apparatus22 so that all of the incoming air must flow through the evaporators 24and 26. Also in this incoming air stream is a filter 30 which removessolid particles from the air stream after the air is passed through theevaporator 24 and 26. This air circulation is provided by a fan 32driven by an electric motor 34 which also drives the condenser fan 36.The air which is drawn through the evaporators 24 and 26 and the filter30 by the fan 32 is discharged back into the room through the openings38 and 40. A partition wall 42 of thermal insulating material dividesthe air cooling portion of the apparatus from the refrigerant liquefyingportion.

The refrigerant liquefying portion comprises a motor compressor 44 whichwithdraws evaporated refrigerant from the upper manifold of the lowerevaporator 24 through the suction conduit 46 and compresses and forwardsthe compressed refrigerant to the condenser 48 Where the refrigerant iscondensed and returned through a capillary tube restrictor 50 to thebottom manifold of the lower evaporator 24. A similar motor compressorunit 52 is provided for withdrawing evaporated refrigerant from theupper manifold of the upper evaporator 26 through the suction conduit54. This evaporated refrigerant is compressed by the motor compressorunit 52 and forwarded to the condenser 55 where the compressedrefrigerant is liquefied and returned through the capillary tuberestrictor 58 to the bottom manifold of the upper evaporator 26. Thecondenser fan 36 draws air from the exterior of the room 60 through theopenings 52 and 64 for cooling both compressors and both condensersafter which the air is discharged directly to the outside atmosphere.

The motor 34 is connected by the conductors 68 to the conductors 68 andI so that the fans 32 and 35 operate continuously. It has been foundwhen such apparatus reaches a temperature below which it is designed tooperate such as 70 F., but under certain conditions of humidity, frostbegins to accumulate upon the lower rear tubes of the lower exaporator24. Continued operation under such conditions causes the frost and iceto gradually accumulate so as to seriously block the flow of air throughthe lower evaporator 24. The increased restriction of the air flowthrough the lower evaporator 24 increases the rate of frost and iceaccumulation so that the situation becomes progressively worse as longas the adverse conditions continue. When the situation is discovered andthe air conditioning apparatus is shut down, there is a considerableamount of ice which must melt before the operation of the apparatus canbe resumed. The frost and ice water resulting from this meltingsometimes overflows the facilities provided for the collecting anddisposal of water condensed from the air and may drip upon the floor.Sometimes this overflow or dripping is caused by freezing or clogging ofdrainage facilities by the ice and frost.

To prevent such undesirable situations, I have provided a simple bellowsactuated snap-acting thermostat I2 which may be of the type shown inPatent 2,479,047 having its contacts 14 connected in series with thesupply conductor I6 which with the supply conductor I8 supplies themotor compressor unit 44 with electric energy. The thermostat 12 has theend of its temperature sensitive capillary tube 89 formed into aserpentine shape so as to serve as a bulb which is wrapper around thelower rear return bend 82 of the lower evaporator 24. This lower rearreturn bend 82 is the coldest portion of the evaporator and is the placeat which the frost and ice first begins to accumulate. The reasonforthis is that it is furtherest from the incoming warm air which entersfrom the opening 28 and has less heat transfer with the air because ofthe absence of fins upon the return bend. As shown in detail in Fig. 2,the clamping of the capillary tube 80 to the return bend 82 isaccomplished by a pair of plates 84 and a bolt 86 which extends throughaperture in the plates 84 and through the inside of the return bend 82.

As shown by the temperature-time chart Fig. 3, the thermostat I2 is setto open when the temperature sensitive capillary tube 80 reaches atemperature of 35 F. and it is set to 'reclose when the evaporatortemperature reaches 60 F. As shown by the chart, when the apparatus isstarted the room air and the evaporator temperature are very nearly thesame. The evaporator temperature, however, falls more rapidly than theroom air temperature and after about three and one-half hours ofcontinuous operation, the evaporator temperature is reduced to about 35F. while the room air temperature is reduced to about 68 F. If operationof the apparatus were continued these temperatures would fall stilllower and frost and ice would begin to accumulate. However, since thethermostat I2 is set to open at 35 F. the lower evaporator 24 will bedisabled thereby causing the evaporator 24 to begin to warm up. The roomairtemperature will also warm up due to the reduced cooling effect. Thefans 32 and 36 however, continue to operate and the upper refrigeratingsystem may likewise continue to operate. Cycling of the lowerrefrigerating system will continue on this basis as long as thetemperature is at such a low level. In this way frosting is preventedand maximum trouble-free use of the apparatus is obtained.

Ordinarily, no frosting or freezing of the upper evaporator 26 isencountered. However this upper system, if desired, may be controlled bya simple room thermostat 88 having contacts 90 which are connected inseries with one of the conductors 92 providing a connection between thesupply conductor 68 and the upper motor compressor unit 52. The secondconductor 94 provides a second connection between the motor compressorunit 52 and the supply conductor 10. This room thermostat I3 8 willlimit the temperature to which the room 60 will 'be cooled.

In Fig. Sthere is shown an air conditioning apparatus ZI2I forde'humidification of aroom or basement. It is provided with acylindrical casing I23 which is adapted to be placed. over a drain.Within the cylindrical casing 1.23., there is provided a sealed motorcompressor unit I215. Beneath the motor compressor unit I25 thereprovided a condenser I21 formed of tubing in the shape of a flat conicalspiral and directly beneath it is an evaporator I29 likewise in theshape of .a flat conical spiral. The motor compressor unit I25withdrawsevaporated refrigerant from the outside turn :of the evaporator429 through the suction conduit I3I and-compresses this refrigerant andforwards the compressed refrigerant through the supply ocnduit 433 tothe outside turn of the condenser I2 1. The innermost turns of thecondenser I21 and the evaporator I29 are connected by a capillary tubewestrictor I35 which controls the flow of liquid refrigerant from thecondenser 1 -21 to the-evaporator [29.

Above the sealed motor compressor unit Hi, there is provided a fan I31driven by the electric motor I39 connected by the conductors 14.4directly to the electric :powersupply so that the fan I-3I will beoperated continuously. The fan i3] draws air from the room or basemeritthrough the openings 143 in the bottom of the casing I23 and thencethrough the coils :of the evaporator I29. On the cold sur iaces of theevaporator coils I29, moisture is condensed from the air and thiscondensed moisture is collected by the drip collector I45 having acentral discharge opening "I41 which is placed -over the drain fordisposal of the condensed moisture. The air, after passing through thecoils of the evaporator 129 is then reheated "by the coils of thecondenser I21 and discharged-badk into the room or basement through theseries of outlet openings I43 provided in the top of the cylin dricalcasing I23.

It has been found that when such'an apparatus is placed in very 'coldbasements and operated continuously, that frost and ice begin to"collect upon the outermost turns of the evaporator I29 after .a longperiod of operation As shown in Fig. 4, the evaporator, temperaturefalls below 30 F. after about eleven or twelve years of continuousoperation in a rather cool basement.

However, since the condenser IN is such close proximity to theevaporator I29 the frost does not begin to build up until lowertemperatures are reached. To prevent this accumulation of frost and ice,I connect a simple bellows actuated snap acting thermostat I5I which maybe of the type shown in Patent 2,479,047 having its contacts I53connected in series with one of the supply conductors I55 of the motorcompressor unit I25. The temperature sensitive capillary tube I51connected to the bellows of this thermostat I5I hasits end portion I59formed into a serpentine shape'and clamped on top of the second andthird outermost turns of the coils of the evaporator- I29. The secondand third outermost turns are the coldest turns in this evaporator andtherefore are the first to frost. Y

The clamping is done by a sheet metal clamp IBI which extends over theserpentine end portion I59 of the capillary tube I57 and the second andthird outermost turns of the evaporator I29. The end portions I63 andIE5 of this clamp I'BI are curled beneath the outermost and the fourthoutermost coil of evaporator I 29. This insures that the operation ofthe thermostat I 5I will be substantially in accordance with thetemperature of the second and third outermost coils of evaporator I29.The thermostat I5I is set to open at about 28 F. which is just above thetemperature at which these coils begin to frost under adverseconditions. The thermostat I5I is set to reclose at about 50 F. as shownin Fig. 4. The room or basement air temperature will fall as long as thesystem operates and will rise when the thermostat I5I opens thecompressor motor circuit. This control arrangement allows maximum useand effectiveness of this air conditioning apparatus fordehumidification and prevents failures by reason of frosting underadverse conditions.

While the form of embodiment of the invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, as may come within the scope of the claims whichfollow.

What is claimed is as follows:

1. A dual air conditioning apparatus for conditioning the air of anenclosure for producing human comfort including fan means forcirculating air from the enclosure through the apparatus and returningthe conditioned air to the enclosure, a first evaporator and a secondevaporator located above the first evaporator in said circulating air,refrigerant liquefying means for supplying liquid refrigerant to and forwithdrawing evaporated refrigerant from said first and secondevaporators, and a thermostatic means having a thermostatic elementclamped to the coldest portion of said first evaporator for disablingsaid first evaporator, and a room thermostat responsive to thetemperature of the air in said enclosure for disabling said secondevaporator.

2. Air conditioning apparatus for conditioning the air of an enclosure,including means for circulating air from the enclosure through theapparatus and returning the conditioned air to the enclosure, anevaporating means located in the apparatus in said circulating air forconditioning in the form of a cross-finned serpentine tubular structurehaving return bends at least at one 6 end thereof located in theapparatus with the cross-fins in and parallelto the flow of thecirculating air for conditioning the circulating air,

a refrigerant. compressing and condensing'means operatively connected tosaid evaporating means, and thermostatic control means for saidcompressing means having a thermostat bulb mounted upon the lowermostreturn bend which is nearest the exit face of the evaporator structurehaving a setting to stop the compressing means when said bulb reaches atemperature just above the temperature at which frost and icebegin'to'form on said evaporating means. l i

3. Anair conditioning unit comprising a casingadapted to be mounted in awindow of an enclosure to be conditioned with one portion of the casingprojecting into the enclosure and another portion projecting out of theenclosure, means separating said casing into an evaporator compartmentand a condenser compartments/first evaporator and a second evaporatorlocated in said evaporator compartment, a first refrigerant liquefyingmeans including a first condenser in said condenser compartment for supplying liquid refrigerant to said first evaporator. a second refrigerantliquefying means including a second condenser in said condensercompartment for supplying liquid refrigerant to said second evaporator,and means for stopping said first refrigerant liquefying means inresponse to the temperature of said first evaporator falling below apredetermined value.

4. An air conditioning unit comprising a casing adapted to be mounted ina window of an enclosure to be conditioned with one portion of thecasing projecting into the enclosure and another portion projecting outof the enclosure, means separating said casing into an evaporatorcompartment and a condenser compartment, a first evaporator and a secondevaporator located in said evaporator compartment, a first refrigerantliquefying means including a first condenser in said condensercompartment for supplying liquid refrigerant to said first evaporator, asecond refrigerant liquefying means including a second condenser in saidcondenser compartment for supplying liquid refrigerant to said secondevaporator, means for stopping said first refrigerant liquefying meansin response to the temperature of said first evaporator falling below apredetermined value, and means responsive to the temperature of the airin said enclosure for controlling said second refrigerant liquefyingmeans.

5. An air conditioning unit comprising a casing adapted to be mounted ina window of an enclosure to beconditioned with one portion of the casingprojecting into the enclosure and another portion projecting out of theenclosure, means separating said casing into an evaporator compartmentand a condenser compartment, a first evaporator and a second evaporatorlocated in said evaporator compartment, a first refrigerant liquefyingmeans including a first condenser in said condenser compartment forsupplying liquid refrigerant to said first evaporator, a secondrefrigerant liquefying means including a second condenser in saidcondenser compartment for supplying liquid refrigerant to said secondevaporator, means for stopping said first refrigerant liquefying meansin response to the temperature of said first evaporator falling below apredetermined value, means responsive to the temperature of the air insaid enclosure for controlling said second refrigerant liquefying means,

and a continuously operating fan for circulating air over both of saidevaporators in unison.

6. An air conditioning unit comprising a casing adapted to be mounted ina window of an enclosure to be conditioned with one portion of thecasing projecting into the enclosure and another portion projecting outof the enclosure, means separating said casing into an evaporatorcompartment and a condenser compartment,

a first evaporator and a second evaporator located 10 in said evaporatorcompartment, a first refrigerant liquefying means including a firstcondenser in said condenser compartment for supplying liquid refrigerantto said first evaporator, a second refrigerant liquefying meansincluding a second condenser in said condenser compartment for supplyingliquid refrigerant to said second evaporator, means for stopping saidfirst refrigerant liquefying means in response to the temperature ofsaid first evaporator falling below a predetermined value, meansresponsive to the temperature of the air in said enclosure forcontrolling said second refrigerant liquefying means, and a common fanfor circulating air to be conditioned over said evaporators, saidevaporators being arranged in parallel relative to the circulatins air.

References Cited in the file of this patent UNITED STATES PAI'ENTSNumber Name Date 1,967,420 Muffly July 24, 1934 1,988,319 King Jan. 15,1935 1,988,552 Greever Jan. 22, 1935 2,049,413 Cannon Aug. 4, 19362,313,390 Newton Mar. 9, 1943 2,332,711 Gould Oct. 26, 1943 2,367,305Newton Jan. 16, 1945 2,388,210 Hanson Oct. 30, 1945 2,451,682 Lund Oct.19, 1948 2,499,411 Pennington Mar. 7, 1950 2,513,679 Ritter July 4, 1950

